The present invention relates to semiconductor integrated circuit devices and, more particularly, to a technique which may effectively be applied to semiconductor integrated circuit devices having MISFETs.
It is a known practice to adopt the LDD (Lightly Doped Drain) structure in order to relax the electric field at the drain end of N-channel MISFET. In the LDD structure, the low-concentration region of the drain on the side thereof which is closer to the channel region is formed using phosphorus, which has a relatively large diffusion coefficient.
Techniques concerning MISFETs having the LDD structure are described, for example, in "Microdevices", an extra issue of Nikkei Electronics, Aug. 22, 1983, Nikkei McGraw-Hill, p. 82-86.